Platelet glycoprotein VI dependent microparticle formation

描述（由申请人提供）：（GP）VI是胶原蛋白的两种主要初级血小板受体之一，胶原蛋白是流动血液和受损血管系统界面处的关键配体。GPVI与血小板功能的相关性已经通过抑制性抗体、转基因小鼠、人类遗传多态性和突变建立。用纤维状胶原刺激血小板导致血小板聚集和血小板微粒（小于1 μ m的血小板碎片）的急剧释放。我们将证明释放的微粒介导的配体结合到血小板GPVI。除了胶原蛋白与止血和血栓形成的相关性之外，GPVI和血小板微粒的存在最近已被证明会加剧鼠类模型中的类风湿性关节炎。与人类疾病的联系是在患病的滑液中每升存在多达400，000个血小板微粒。因此，血小板微粒代表类风湿性关节炎患者滑液中的主要细胞组分。GPVI或其相关亚基FcR-基因缺失可改善类风湿性关节炎小鼠模型的疾病已观察到患病人滑液中存在的血小板微粒数量的变化，但这种变化的机制基础或生理相关性尚不清楚。我们建议解决GPVI生物学翻译的一个主要差距，我们的理解和治疗类风湿性关节炎。首先，存在影响GPVI依赖性信号转导途径的已知GPVI单倍型。我们对血小板微粒是否以及如何受到特定GPVI单倍型影响的理解存在差距。其次，一个主要的问题是GPVI的表达和功能是否会影响类风湿关节炎的严重程度。为了解决这些问题，我们提出1）表征来自定义的GPVI单倍型的正常人样品的血小板微粒产生，和2）记录患有表现出从最小到极端严重程度的疾病的类风湿性关节炎患者的患者队列中的GPVI单倍型。拟议研究的结果可能会影响类风湿性关节炎治疗的临床实践范例，这些机制可能与其他自身免疫依赖性炎症（如哮喘）相关。因此，拟议的研究测试了寻求建立止血、血栓形成和炎症联系的新范例的新假设。

DESCRIPTION (provided by applicant): (GP) VI is one of two major primary platelet receptors for collagen, a critical ligand at the interface of flowing blood and damaged vasculature. The relevance of GPVI to platelet function has been established with inhibitory antibodies, genetically modified mice, human genetic polymorphisms, and mutations. Stimulation of platelets with fibrillar collagen leads to platelet aggregation and a dramatic release of platelet microparticles (platelet fragments of less than 1 m). We will demonstrate the release of microparticles is mediated by ligand binding to platelet GPVI. Beyond the relevance of collagen to hemostasis and thrombosis, GPVI and the presence of platelet microparticles has recently been shown to exacerbate rheumatoid arthritis in murine models. The link to human disease is the presence of up to 400,000 platelet microparticles per l in diseased synovial fluid. As such, the platelet microparticle represents the major cellular component in synovial fluid from rheumatoid arthritis patients. Genetic deletion of GPVI or its associated subunit, FcR- , ameliorates disease in mouse models of rheumatoid arthritis. Variation in the number of platelet microparticles present in diseased human synovial fluid has been observed but the mechanistic basis or physiologic relevance for this variation is unknown. We propose addressing a major gap in the translation of GPVI biology to our understanding and treatment of rheumatoid arthritis. First, known GPVI haplotypes exist that effect GPVI-dependent signal transduction pathways. A gap exists in our understanding for whether and how platelet microparticles are influenced by specific GPVI haplotypes. Secondly, a major question exists as to whether GPVI expression and function can influence the severity of rheumatoid arthritis. To address these issues, we propose 1) to characterize platelet microparticle production from normal human samples of defined GPVI haplotypes and 2) document GPVI haplotypes in a cohort of patients with rheumatoid arthritis patients exhibiting disease from minimal to extreme severity. The outcome of the proposed studies could impact clinical practice paradigms for the treatment of rheumatoid arthritis with the possibility these mechanisms are relevant to other autoimmune-dependent inflammations, such as asthma. Thus, the proposed studies test novel hypotheses seeking to establish new paradigms linking hemostasis, thrombosis and inflammation.